In general, a mobile communication system is developed to provide voice communication service while guaranteeing activity of users. However, the mobile communication systems may include a data providing service beyond the voice communication service and may provide a high speed data service. In spite of such a development, current mobile communication systems are undergoing a deficiency of resources and should further improve their performance due to the needs of users for a service of a higher speed.
Long Term Evolution-Advanced (LTE-A) in the 3rd Generation Partnership Project (3GPP) is a technology implementing a high speed packet-based communication having a transmission speed including 1 Gbps. Further, in LTE-A, all the cells accessible by a UE have the same duplex structure. Therefore, all the cells may have a Frequency Division Duplex (FDD) structure or may have a Time Division Duplex (TDD) structure. The TDD structure may be a static TDD structure, in which an Uplink-Downlink (UL-DL) configuration is maintained, or a dynamic TDD structure, in which the UL-DL configuration is changed by system information, a higher layer signal, or a downlink common control channel.
If one cell controlled by an evolved Node B (eNB) has an FDD structure and a single frequency band is added to the FDD structure, it is easy to apply a TDD structure to the added single frequency band because two different frequency bands are needed for the downlink and the uplink, respectively, in order to operate the FDD structure. Therefore, there is a need for a scheme for transmitting a control channel for data transmitted from a plurality of cells when the cells have different duplex schemes due to the addition of limited frequency bands as described above or other reasons.
The LTE-A employs a scheme which increases the number of cells accessible by a UE while allowing feedback occurring in respective cells to be transmitted in only a Primary cell, which may be referred to as a P cell or Pcell. Specifically, a UE capable of supporting only one carrier in the uplink transmits an uplink control channel by using only one uplink carrier. Therefore, even when a UE capable of supporting a plurality of carriers in the uplink and a UE capable of supporting only one carrier in the uplink coexist, the LTE-A, which does not include many UEs capable of supporting a plurality of carriers within an eNB, has employed a method allowing feedback occurring in the downlink of each cell to be transmitted in only a primary cell, in order to define a standard for supporting all UEs.
However, when the number of UEs supporting a plurality of uplink carriers increases, transmission of an uplink control channel through a plurality of uplink carriers should be supported. Further, there is a need for a technology in which an eNB schedules uplink data to a UE and transmits a downlink control channel for the uplink data to the UE, according to a capability of a UE supporting an uplink carrier.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.